In any case it seems like the XFS driver in 2.6.18-rc1 is decently broken.After booting into 2.6.17 again, I could use /usr again but random filescontain null bytes, firefox segfaults instead of starting up and a number of programs fail in mysterious ways. I tried to recover using xfs_repairbut I feel that my partition is thorougly borked. Of course no data was lost due to backups but still I'd like this bug to be fixed ;-)

If more information from my logs is required, I can make it available (and anypart of the partition if required).